Error detection/correction and fault detection/recovery – Pulse or data error handling – Digital data error correction
Reexamination Certificate
2000-04-28
2004-05-04
Baker, Stephen M. (Department: 2133)
Error detection/correction and fault detection/recovery
Pulse or data error handling
Digital data error correction
C714S755000, C714S769000, C714S809000
Reexamination Certificate
active
06732320
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to optical media, and more particularly to error correction in optical media data processing.
BACKGROUND OF THE INVENTION
Data formats for optical drives and media are well known in the art. According to the standard of the industry, set forth in what is commonly referred to as the “Red Book”, data for optical drives are in a 8 bit format, while the data stored on the optical media are in a 14 bit format. Thus, when data is to be written onto an optical media, it is first modulated from the 8 bit format to the 14 bit format. This modulation process is commonly referred to as “EFM” or Eight to Fourteen Modulation. Conversely, when data is retrieved from an optical media, it must first be demodulated from the 14 bit format to the 8 bit format before the data may be further processed.
Two conventional demodulation processes are provided by the Red Book. The first conventional process is to use an EFM conversion table.
FIG. 1
illustrates the standard EFM conversion table. With this first process, the 14 bit data (C
1
-C
14
) is mapped into an 8 bit data (d
1
-d
8
) according to the EFM conversion table. However, errors may occur in the mapping. For example, since the 14 bit format provides more combinations of 1's and 0's than the 8 bit format, an error occurs when a 14 bit data does not have a corresponding 8 bit data in the EFM conversion table or when a wrong entry due to a violation of the run length (RLL) requirement. These errors may be found and corrected by the Error Correction Code (ECC). The ECC uses information encoded during the C
1
and C
2
encoding processes to find and correct errors. The C
1
and C
2
encoding processes are performed prior to the writing of the data onto the optical media. In the C
1
encoding process, additional bytes are encoded containing information about the data. In the C
2
encoding process, additional bytes are encoded into the C
1
encoded data, and the frames of the C
2
encoded data are interleaved with an appropriate time delay.
After the demodulation process, if one error only is found, then this error is correctable using during the C
1
correction process. Mathematically, the C
1
encoded data can only guarantee the correction of one error.
The second conventional process is to use a logic array to convert the data from the 14 bit format to the 8 bit format.
FIG. 2A
illustrates a conventional demodulator
250
with the logic array
252
. C
i
is the input data in the 14 bit format. D
i
is the output data in the 8 bit format.
FIG. 2B
shows the product term input bits and the corresponding active outputs for the logic array
252
. This is process, all data is processed through the logic array
252
. When there is an error, a “best guess” value results from the logic array
252
. However, there is no awareness that the error occurred. Thus, no further data correction can be implemented. This process also limits the integrity of the read data.
Accordingly, there exists a need for an improved method and system for error correction in optical media data processing. The improved method and system should be easy to implement and increase the integrity of the read data. The present invention addresses such a need.
SUMMARY OF THE INVENTION
The present invention provides a method and system for error correction in optical media data processing. The method includes demodulating a data using a conversion table; marking errors which occur during the demodulation; utilizing estimated values for the marked errors; and performing error correction. The method and system marks errors which occur during demodulation. A logic array is used to obtain estimated values for the marked errors. The marking of errors and the use of values from the logic array for the marked errors increases the probability of the C
1
and C
2
correction processes being able to correct the errors. Fewer “not correctable” data results. This increases the integrity of the read data.
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Baker Stephen M.
ProMOS Technologies Inc.
Sawyer Law Group LLP
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